#include <asm.h>
#include <csr.h>
#include <asm/regs.h>

.macro SAVE_CONTEXT
  /* TODO: [p2-task3] save all general purpose registers here! */
  /* HINT: Pay attention to the function of tp and sp, and save them carefully! */

  sd   sp, PCB_USER_SP(tp) //store the user_sp to the user_sp field int the pcb_t
  ld   sp, PCB_KERNEL_SP(tp) //switch the user_sp to the kernel_sp;
  
  addi sp, sp, SWITCH_TO_SIZE
  
  sd   zero, OFFSET_REG_ZERO(sp)
  sd   ra,   OFFSET_REG_RA(sp)
  sd   sp,   OFFSET_REG_SP(sp)
  sd   gp,   OFFSET_REG_GP(sp)
  sd   tp,   OFFSET_REG_TP(sp)
  sd   t0,   OFFSET_REG_T0(sp)
  sd   t1,   OFFSET_REG_T1(sp)
  sd   t2,   OFFSET_REG_T2(sp)
  sd   s0,   OFFSET_REG_S0(sp)
  sd   s1,   OFFSET_REG_S1(sp)
  sd   a0,   OFFSET_REG_A0(sp)
  sd   a1,   OFFSET_REG_A1(sp)
  sd   a2,   OFFSET_REG_A2(sp)
  sd   a3,   OFFSET_REG_A3(sp)
  sd   a4,   OFFSET_REG_A4(sp)
  sd   a5,   OFFSET_REG_A5(sp)
  sd   a6,   OFFSET_REG_A6(sp)
  sd   a7,   OFFSET_REG_A7(sp)
  sd   s2,   OFFSET_REG_S2(sp)
  sd   s3,   OFFSET_REG_S3(sp)
  sd   s4,   OFFSET_REG_S4(sp)
  sd   s5,   OFFSET_REG_S5(sp)
  sd   s6,   OFFSET_REG_S6(sp)
  sd   s7,   OFFSET_REG_S7(sp)
  sd   s8,   OFFSET_REG_S8(sp)
  sd   s9,   OFFSET_REG_S9(sp)
  sd   s10,  OFFSET_REG_S10(sp)
  sd   s11,  OFFSET_REG_S11(sp)

  /*
   * Disable user-mode memory access as it should only be set in the
   * actual user copy routines.
   *
   * Disable the FPU to detect illegal usage of floating point in kernel
   * space.
   */
  li t0, SR_SUM | SR_FS

  /* TODO: [p2-task3] save sstatus, sepc, stval and scause on kernel stack */

  csrr a0, sstatus
  sd   a0, OFFSET_REG_SSTATUS(sp)
  csrr a0, sepc
  sd   a0, OFFSET_REG_SEPC(sp)
  csrr a0, stval
  sd   a0, OFFSET_REG_SBADADDR(sp)
  csrr a0, scause
  sd   a0, OFFSET_REG_SCAUSE(sp)

  addi sp, sp, -SWITCH_TO_SIZE


.endm

.macro RESTORE_CONTEXT
  /* TODO: Restore all general purpose registers and sepc, sstatus */
  /* HINT: Pay attention to sp again! */

  ld sp, PCB_KERNEL_SP(tp)
  addi sp, sp, SWITCH_TO_SIZE

  ld   zero, OFFSET_REG_ZERO(sp)
  ld   ra,   OFFSET_REG_RA(sp)
  ld   gp,   OFFSET_REG_GP(sp)
  //ld   tp,   OFFSET_REG_TP(sp)
  ld   t0,   OFFSET_REG_T0(sp)
  ld   t1,   OFFSET_REG_T1(sp)
  ld   t2,   OFFSET_REG_T2(sp)
  ld   s0,   OFFSET_REG_S0(sp)
  ld   s1,   OFFSET_REG_S1(sp)
  ld   a0,   OFFSET_REG_A0(sp)
  ld   a1,   OFFSET_REG_A1(sp)
  ld   a2,   OFFSET_REG_A2(sp)
  ld   a3,   OFFSET_REG_A3(sp)
  ld   a4,   OFFSET_REG_A4(sp)
  ld   a5,   OFFSET_REG_A5(sp)
  ld   a6,   OFFSET_REG_A6(sp)
  ld   a7,   OFFSET_REG_A7(sp)
  ld   s2,   OFFSET_REG_S2(sp)
  ld   s3,   OFFSET_REG_S3(sp)
  ld   s4,   OFFSET_REG_S4(sp)
  ld   s5,   OFFSET_REG_S5(sp)
  ld   s6,   OFFSET_REG_S6(sp)
  ld   s7,   OFFSET_REG_S7(sp)
  ld   s8,   OFFSET_REG_S8(sp)
  ld   s9,   OFFSET_REG_S9(sp)
  ld   s10,  OFFSET_REG_S10(sp)
  ld   s11,  OFFSET_REG_S11(sp)
  
  ld   a0, OFFSET_REG_SSTATUS(sp)
  csrw sstatus, a0
  ld   a0, OFFSET_REG_SEPC(sp)
  csrw sepc, a0

  ld   a0, OFFSET_REG_A0(sp)
  ld   sp, PCB_USER_SP(tp)

  


  
.endm

ENTRY(enable_preempt)
  not t0, x0
  csrs CSR_SIE, t0
  jr ra
ENDPROC(enable_preempt)

ENTRY(disable_preempt)
  csrw CSR_SIE, zero
  jr ra
ENDPROC(disable_preempt)

ENTRY(enable_interrupt)
  li t0, SR_SIE
  csrs CSR_SSTATUS, t0
  jr ra
ENDPROC(enable_interrupt)

ENTRY(disable_interrupt)
  li t0, SR_SIE
  csrc CSR_SSTATUS, t0
  jr ra
ENDPROC(disable_interrupt)

// NOTE: the address of previous pcb in a0
// NOTE: the address of next pcb in a1
ENTRY(switch_to)
  
  ld t0, PCB_KERNEL_SP(a0)

  /* TODO: [p2-task1] save all callee save registers on kernel stack,
   * see the definition of `struct switchto_context` in sched.h*/
  sd ra,  SWITCH_TO_RA(t0)
  sd sp,  SWITCH_TO_SP(t0)
  sd s0,  SWITCH_TO_S0(t0)
  sd s1,  SWITCH_TO_S1(t0)
  sd s2,  SWITCH_TO_S2(t0)
  sd s3,  SWITCH_TO_S3(t0)
  sd s4,  SWITCH_TO_S4(t0)
  sd s5,  SWITCH_TO_S5(t0)
  sd s6,  SWITCH_TO_S6(t0)
  sd s7,  SWITCH_TO_S7(t0)
  sd s8,  SWITCH_TO_S8(t0)
  sd s9,  SWITCH_TO_S9(t0)
  sd s10, SWITCH_TO_S10(t0)
  sd s11, SWITCH_TO_S11(t0)


  /* TODO: [p2-task1] restore all callee save registers from kernel stack,
   * see the definition of `struct switchto_context` in sched.h*/
  
  ld t0, PCB_KERNEL_SP(a1)

  ld ra,  SWITCH_TO_RA(t0)
  ld sp,  SWITCH_TO_SP(t0)
  ld s0,  SWITCH_TO_S0(t0)
  ld s1,  SWITCH_TO_S1(t0)
  ld s2,  SWITCH_TO_S2(t0)
  ld s3,  SWITCH_TO_S3(t0)
  ld s4,  SWITCH_TO_S4(t0)
  ld s5,  SWITCH_TO_S5(t0)
  ld s6,  SWITCH_TO_S6(t0)
  ld s7,  SWITCH_TO_S7(t0)
  ld s8,  SWITCH_TO_S8(t0)
  ld s9,  SWITCH_TO_S9(t0)
  ld s10, SWITCH_TO_S10(t0)
  ld s11, SWITCH_TO_S11(t0)
  
  
  addi tp, a1, 0

  jr ra
ENDPROC(switch_to)

ENTRY(ret_from_exception)
  /* TODO: [p2-task3] restore context via provided macro and return to sepc */
  /* HINT: remember to check your sp, does it point to the right address? */

  RESTORE_CONTEXT
  sret

ENDPROC(ret_from_exception)

ENTRY(exception_handler_entry)

  /* TODO: [p2-task3] save context via the provided macro */

  SAVE_CONTEXT

  /* TODO: [p2-task3] load ret_from_exception into $ra so that we can return to
   * ret_from_exception when interrupt_help complete.
   */
  la ra, ret_from_exception

  /* TODO: [p2-task3] call interrupt_helper
   * NOTE: don't forget to pass parameters for it.
   */
  addi a0, sp, SWITCH_TO_SIZE
  csrr a1, stval
  csrr a2, scause
  call t1, interrupt_helper
  

ENDPROC(exception_handler_entry)
